It is presently known that the braking systems of many vehicles include wheel speed transducers or sensors for determining the instantaneous wheel speed of the various wheels of the vehicle. Such wheel speed transducers are particularly important in aircraft braking systems where maximum braking efficiency is desired. Known wheel speed transducers convert the rotational speed of the associated wheel to electrical signals. This wheel speed signal is then employed by brake control circuitry such as antiskid control circuitry and/or automatic brake control circuitry to control the braking activity of the vehicle.
The pulse generators of wheel speed transducers typically include one part which is fixed to the axle or aircraft frame, while another part is connected to and rotates with the associated wheel. Accordingly, a coupler is required to interconnect the rotatable member to the wheel.
Previously known couplers have been characterized by a number of shortcomings which adversely impact the operability, accuracy, and life of the coupler and transducer unit. Excessive backlash or uncoupled movement between the input and the output of the coupler has previously been the result of an inability to tightly mate the coupler portions due to necessary tolerances, clearances, and the like. This backlash problem has given rise to spurious and inaccurate signal outputs from the transducer resulting, in large part, from the fact that the input and output portions of the coupler do not constantly rotate in unison, but lead/lag conditions inherently occur.
Further, previously known couplers have been incapable of accommodating significant misalignments between the coupled input and output portions of the transducer. Such misalignments are characterized as parallel, angular, and axial, respectfully occurring when (1) the inputs and outputs are parallel but offset from each other, (2) the inputs and outputs are not parallel, but angled with respect to each other, and (3) the inputs and outputs are coaxial but inordinately spaced from each other. These misalignments can occur singularly, in various combinations, or all simultaneously.
Further, previously known couplers for wheel speed transducers have typically been undesirably large with respect to physical size and have been characterized by excessive weight, the same being most undesirable in an aircraft environment. Known couplers have also been short lived, given to excessive wear and early degradation of accuracy and consistency, resulting primarily from backlash. Additionally, known wheel speed transducer couplers are not given to ease of assembly to interconnect the transducer between the stationary axle and the rotating wheel. Prior art couplers also have ambient operating temperature limitations due to the material employed thereby.